Product Description
CUMMINS 3947759 OEM VALVE TAPPET (LIFTER) – ISB 5.9L/6.7L (2003–2018)
The Cummins 3947759 valve tappet is the genuine OEM lifter used on modern ISB and QSB engines, including 2003–2018 Ram 2500/3500 5.9L & 6.7L common-rail applications. Each tappet is manufactured to Cummins specifications for hardness, geometry, and finish so your cam lobes and valve train live a long, quiet life.
This part is sold individually. A complete ISB 5.9L/6.7L engine requires 12 tappets.
Key Features
- Genuine Cummins OEM valve tappet (lifter) for ISB and QSB engines.
- Designed for 2003–2018 Ram 5.9L & 6.7L ISB common-rail platforms.
- Flat mechanical tappet with wide footprint for excellent lobe contact and durability.
- Hardened and ground to Cummins specs to protect the camshaft from scuffing and pitting.
- Direct drop-in with OEM pushrods and rocker gear—no modifications required.
- Sold each so you can replace a single lifter or order 12 for a full set.
Fitment
Automotive – Dodge/Ram Trucks
Fits the following Ram applications (verify by Engine Serial Number for special cases):
- 2003–2007 Ram 2500/3500 with 5.9L ISB 24-valve common-rail Cummins
- 2007.5–2018 Ram 2500/3500 with 6.7L ISB 24-valve common-rail Cummins
Industrial / Off-Highway (Typical)
Commonly used on later ISB and QSB platforms. Always confirm by ESN before ordering:
- Cummins ISB4.5 and ISB6.7 (various on-highway and vocational equipment)
- Cummins QSB4.5 and QSB6.7 off-highway, construction, and industrial engines
Important Fitment Notes:
- Designed for 2003+ common-rail ISB/QSB engines. Earlier 24-valve (1998.5–2002) and 12-valve applications may only use this tappet when the camshaft does not have a mechanical lift-pump eccentric. Always check cam design and ESN.
- Not intended for camshafts with a mechanical fuel-pump lobe.
Cross-Reference & Alternatives
- Supersedes Cummins part number 4891226.
- Common aftermarket cross-reference for identification: PAI 191859 (check specs before mixing brands).
- Aftermarket OE-style alternative:
INTERSTATE-MCBEE M-3947759 VALVE TAPPET 03–18 5.9L/6.7L CUMMINS (AFTERMARKET REPLACEMENT) - Performance upgrade options:
Specifications
Specifications for CUMMINS 3947759
| Parameter | Value |
|---|---|
| Brand | Cummins |
| Cummins Part Number | 3947759 |
| Supersedes | 4891226 (verify by ESN) |
| Component Type | Valve tappet (lifter), flat mechanical cam follower |
| Outside Diameter | Approx. 1.50 in (38.1 mm) |
| Engine Families (typical) | ISB 5.9L & 6.7L common-rail, ISB4.5, QSB4.5, QSB6.7 (ESN verification required) |
| Automotive Applications | 2003–2007 Ram 2500/3500 5.9L ISB; 2007.5–2018 Ram 2500/3500 6.7L ISB |
| Quantity Required per Engine | 12 (sold individually) |
| Material / Finish | Hardened steel tappet body with precision-ground face |
| Typical Shipment Weight | Approx. 0.28 lb per tappet |
| Country of Origin | Varies by production lot (contact us for current COO) |
What’s Included
- (1) Genuine Cummins valve tappet (part number 3947759)
Installation Notes
- Inspect all cam lobes for scoring, flaking, or measurable wear before installing new tappets.
- Always use assembly lube on tappet faces and cam lobes during reassembly.
- Best practice is to replace all 12 tappets together any time a camshaft is replaced.
- Set valve lash to factory spec after initial start-up and again after the first heat cycle.
- Always confirm fitment by Engine Serial Number (ESN) for industrial and mixed-year applications.
FAQ
How many of these tappets does my engine need?
An ISB 5.9L or 6.7L Cummins uses 12 valve tappets. This part is sold individually, so order quantity 12 for a complete engine set.
Does this part replace Cummins 4891226?
Yes. Part number 3947759 is commonly listed as the current Cummins replacement for older number 4891226 in ISB/QSB applications. Always confirm by ESN to be sure.
Will this fit my 1998.5–2002 24-valve Cummins?
This tappet is designed for common-rail ISB platforms (2003 and newer). Some builders use it on earlier engines only when the camshaft has no mechanical lift-pump lobe. If you have a VP44-era 24-valve, verify your cam design and ESN before ordering.
Is this an OEM Cummins part or aftermarket?
This listing is for a genuine Cummins valve tappet with OEM geometry, metallurgy, and surface hardening. For a lower-cost aftermarket option, see the Interstate-McBee M-3947759 tappet listed in the Cross-Reference section above.
Do I need to replace the camshaft when I install new tappets?
If the cam lobes show significant wear, scoring, or pitting, the safest approach is to replace the camshaft and all 12 tappets together. Installing new tappets on a badly worn cam can lead to rapid failure.
Can I keep my stock pushrods with these lifters?
Yes. These are stock-geometry tappets and are designed to run with OEM-length pushrods and rocker arms. Replace pushrods if they are bent, worn, or if you’re upgrading to a high-spring-pressure performance valvetrain.
